Nobody needs POSIX conformance in an interactive pager; that's just conformance for the sake of conformance. Or do they? What is the economic justification ("business case") for working on POSIX compliance in a "more" command?
You should never invoke "more" directly in a script anyway, but rather observe the PAGER environment variable, and fall back on a plain "more" only if that isn't set. (Speaking of which, PAGER isn't described in POSIX, oops!)
If the user wants the pager to exit when the last line is reached, the user can specify the necessary option in PAGER, if their pager supports it. PAGER just has to be properly expanded: treated as a command, not a command name.
You should never invoke "more" directly in a script anyway, but rather observe the PAGER environment variable, and fall back on a plain "more" only if that isn't set. (Speaking of which, PAGER isn't described in POSIX, oops!)
If the user wants the pager to exit when the last line is reached, the user can specify the necessary option in PAGER, if their pager supports it. PAGER just has to be properly expanded: treated as a command, not a command name.